Page 327 - Fundamentals of Air Pollution 3E

III. Meteorological Conditions during Historic Pollution Episodes 283

F. Air Pollution Emergencies
Government authorities increasingly are facing emergencies that may
require lifesaving decisions to be made rapidly by those on the scene. Of
increasing frequency are transportation accidents involving the movement
of volatile hazardous materials. A railroad derailment accident of a tank
car of liquefied chlorine on February 26, 1978, at Youngtown, Florida, in
which seven people died, and an accident in Houston, Texas, involving a
truck carrying anhydrous ammonia on May 11, 1976, which also claimed
seven lives, are examples. Two potentially dangerous situations involved
barges with tanks of chlorine: one which sank in the lower Mississippi
River and another which came adrift and came to rest on the Ohio River
dam at Louisville, Kentucky; neither resulted in release of material.
Releases of radioactive materials from nuclear power plants have oc-
curred, as at Three-Mile Island, Pennsylvania. In such situations, releases
may be sufficient to require evacuation of residents.
Bhopal, India—On December 2,1984 the contents of a methyl isocyanate
(MIC) storage tank at the Union Carbide India plant in Bhopal became hot.
Pressure in the tank became high. Nearly everything that could go wrong
did. The refrigerator unit for the tank, which would have slowed the reac-
tions, was turned off. After midnight, when the release valve blew, the
vent gas scrubber that was to neutralize the gas with caustic soda failed to
work. The flare tower, which would have burned the gas to harmless by-
products, was down for repairs. As a result many tons of MIC were released
from the tank. The gas spread as a foglike cloud over a large, highly
populated area to the south and east of the plant (7). The number of
fatalitites was in excess of 2000 with thousands of others injured. Although
little is available in the way of meteorological measurements, it is assumed
that winds were quite light and that the atmosphere at this time of day
was relatively stable.
Chernobyl, USSR—On April 26, 1986, shortly after midnight local time,
a serious accident occurred at a nuclear power plant in Chernobyl in the
Ukraine. It is estimated that 4% of the core inventory was released between
April 26 and May 6. Quantities of Cs-137 (cesium) and 1-131 (iodine) were
released and transported, resulting in contamination, primarily by wet
deposition of cesium, in Finland, northern Sweden and Norway, the Alps,
and the northern parts of Greece. Because of temperatures of several thou-
sand K during the explosionlike release, the resulting pollutant cloud is
assumed to have reached heights of 2000 m or more. The estimated south-
east winds at plume level initially moved the plume toward Finland, north-
ern Sweden, and northern Norway. As winds at plume level gradually
turned more easterly and finally north and northwesterly, contaminated
air affected the region of the Alps and northern Greece. A number of
investigators, including Hass et al. (8), modeled the long-range transport